list1 = [1,2,3,2]

a = list1[0]

for i in list1:
    if i > a:
        a = i
print(a)



list2 = [1,2,3,4,'a',1,'b',21]

sum = 0

for i in list2:
    if isinstance(i,int):
        sum = sum + i
print(sum)


x = 5
for i in range(1,x):
    if x % i == 0:
        print("不是素数")
        break
else:
    print("是素数")
 

x = 10
sum = 0
for i in range(2,x+1):
    for j in range(2,i):
        if i % j == 0:
            break
    else:
        sum = sum + 1
print(sum)

